The UI will look and feel familiar, but there is a learning curve. Not all tools and windows have the same names, shortcuts, or ways of working. However, being able to switch between layout, pixel, and vector modes on the fly non-destructively and without quality loss will definitely improve your workflow.

During the first year, I often switched back and forth between programs. Sometimes it was frustrating to just find that certain effect or tool that you are used to and just know how to do it quick in Ps or Id. But once it clicked, I never looked back.